1. NetSilicon & Digi Confidential
NET+OS 6.1 Training
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I2C device topics
Introduction
I2C APIs
I2C examples
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I2C device basic
Simple 4-wire device. Multiple I2C devices can be connected to the same I2C bus.
We support two types (all) I2C devices – I2C Master and I2C Slave.
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Performance
We support 100Kbits/sec or 400Kbits/sec.
Support 7 & 10 bit addressing
Dedicated I/O. No change to the gpio.h
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IC2 Master Interface
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I2C Slave
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7bit addressing format
Slave Address
Data(8Bit) RW A S
1. Received of slave side
2. Transmitted of slave side 1 P
S = Start
A = ACK
P = STOP / Repeat Start
From master to slave
From slave to master
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10bit addressing format
Address Upper
Address Lower RW A
Data(8Bit) S
1. Received of slave side
2. Transmitted of slave side 1 P
S = Start
A = ACK
P = STOP / Repeat Start
From master to slave
From slave to master
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Device Open()
Calls i2c_dev_open()
Example
i2cPort = open("/i2c/0",I2C_SLAVE); or
i2cPort = open("/i2c/0",I2C_MASTER);
I2C device channel: /i2c/0
I2C device mode: I2C_MASTER, or I2C_SLAVE.
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Device close()
Calls i2c_dev_close()
Closes the I2C channel.
Example:
ret = close(fd);
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Device Read()
Calls i2c_dev_read().
int i2c_dev_read(int channel, void * i2cMsg, int notUsed, int * notUsed1);
Note: i2cMsg is pointer to the i2cMsg type.
The i2cMeg will be returned by a read callback function in an ISR. DO NOT access it before it is returned.
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Device Write()
Calls i2c_dev_write().
int i2c_dev_write(int channel, void * i2cMsg, int notUsed, int * notUsed1)
The i2cMsg will be returned by a write callback function in an ISR context.
DO NOT access the message before it is returned.
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Device Ioctl()
Calls i2c_dev_ioctl()
Important flags:
I2C_SET_READ_CALLBACK_FUNC
I2C_SET_WRITE_CALLBACK_FUNC
I2C_SET_CLOCK_SPEED
I2C_SET_GCA_IRQ_ENABLE
I2C_FLUSH_BUFFER
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Other APIs
void MCI2cBuildMsg(MC_I2C_MESSAGE_TYPE* i2cMsg, char* buf, unsigned long bufLength, unsigned char addr);
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I2C Specific….
I2C driver is interrupt driven and the I2C interrupt is part of the BBUS interrupt. After we install the I2C interrupt function, on receiving every data byte and I2C commannd, we will receive an interrupt generated by the I2C IP. The MCI2cInterrupt() function will then be called by the ISR handler. Based on the state of the current I2C bus and whether the Mercury is acting as an I2C Master or Slave, the appropriate function will be called. Please refer to the I2C Master or Slave State machine for ISR handling details.
A semaphore is used to keep multiple I2C port from opening at the same time.
A Event flag is created in the application example; but it is up to the application to decide whether to use it or not. The same applies to the Event flag in the nausbdevapp example as well.
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Example
Typical User application
A typical open function call is
fd = open(“i2c/0”, I2C_MASTER); Or
fd = open(“i2c/0”, I2C_SLAVE);
A typical close function call is
Ret = close(fd);
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Read() Example
Typical usage: The third parameter is ignored.
Ret=Read(fd, i2cMsg, 0x0);
If (ret == -1) printf(“ read failed.\n”);
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Write() example
Typical usage: The third parameter is ignored.
Ret=write(fd, i2cMsg, 0x0);
If (ret == -1) printf(“ write failed.\n”);
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I2C message defination
typedef struct _MESSAGE_TYPE {
char * buffer;
unsigned short address;
unsigned long bufLength; /* size of the buffer */
unsigned long availableDataLen;
MC_I2C_BUFFER_STATE state;
} MC_I2C_MESSAGE_TYPE;
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21. Typical write Callback function
void writeCallBackFunc(MC_I2C_MESSAGE_TYPE * ptrData) {
if (ptrData->state != I2C_INIT)
tx_event_flags_set(&i2cEvent,I2C_WRITE_EVENT_FLAG, TX_OR);
/* free(ptrData); */ }
return;
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22. Typical read callback function
void readCallBackFunc(MC_I2C_MESSAGE_TYPE * ptrData) {
if (ptrData->state != I2C_INIT)
tx_event_flags_set(&i2cEvent,I2C_READ_EVENT_FLAG, TX_OR);
/* free(ptrData); */ }
return;
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Example application
MCI2cBuildMsg(i2cMsg, ptrTemp, 26, 0x60);
ret = write(i2cPort, i2cMsg, 0);
MCInstallIsr (I2C_INTERRUPT, (MC_ISR_HANDLER) MCI2cInterrupt, (void *) 0, 0);
while( 1 /* mySleepCount < 6 */) {
ret = tx_event_flags_get(&i2cEvent, I2C_WRITE_EVENT_FLAG|I2C_READ_EVENT_FLAG, TX_OR_CLEAR, &actualEvent, TX_WAIT_FOREVER); ……
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Important files
Driver: Src/bsp/devices/i2c/*
Example:
Src/examples/nai2capp/itc_test.c
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